1. Field of the Invention
The present invention relates to a continuous process and apparatus for depositing elongated members in a lay-up with each member oriented substantially in the longitudinal direction of the lay-up. The elongated members may subsequently be bonded together into a composite product.
2. Description of Related Art
A product containing oriented elongated members or strands is disclosed in Barnes U.S. Pat. No. 4,061,819. That patent is directed to a composite wood product which utilizes elongated wood strands. In such product wood strands having a length in excess of about 2 feet are coated with a resin and are positioned in substantially parallel relationship in a long form which may have a width of, for example, 12 inches. The strands are deposited with their ends in overlapping relationship to provide a roughly uniform distribution along the length of the form. The strands are then compressed and heated to cure the resin and provide the final structural product which can have a strength equal to prime structural lumber.
In preparation of composite strand products by batch methods, strands can be positioned by hand with no significant loss in strength due to disoriented strands. However, when composite strand products are made using a continuous process, the strands are usually deposited on a moving conveyor belt so that the ends overlap. For example, the leading edge of each strand will tend to overlap with strands preceding it onto the conveyor while the trailing edge of the strand will tend to settle lower into the form. (See, e.g., Champigny U.S. Pat. No. 3,493,021). The angles at which the strands are generally positioned are not random, but rather tend to be similar in both magnitude and direction. Hence, the majority of the strands may be oriented away from the horizontal direction in mutually parallel fashion. Such a lay-up mat has what may be referred to as "card-decking" orientation, in that each strand is at an angle to the longitudinal direction of the lay-up mat. It has been discovered that excessive vertical strand angle may also result in vertical curvature in the continuously compressed product.
In the manufacture of composite products of the type disclosed in Barnes U.S. Pat. No. 4,061,819 regulation of the orientation of the elongated members is important to obtain full product strength. If the strands are positioned at an excessively large angle (either vertically or laterally) to the longitudinal direction of the form, the composite products tend to have less strength than their full strength potential.
As disclosed in the Barnes patent, wood strands which have been cut or split along the grain of the wood are normally used in making composite products. However, when such strands are incorporated in a lay-up mat at significant angles to the horizontal, the product strength is reduced. Therefore, although formation of a composite product on a continuous basis is desirable, the strength of the composite product may be significantly lowered from the full strength potential.
It is an object of this invention to provide a continuous method for manufacturing a composite product in which elongated members are oriented substantially parallel to the longitudinal direction of the composite product.
It is a further object of this invention to provide a continuous method of manufacturing a composite product substantially free of vertical curvature in which elongated members are oriented substantially parallel to the longitudinal direction of the composite product.
It is another object of this invention to provide a continuous method for manufacturing composite structural lumber made up of elongated wood strands.
It is still another object of this invention to provide apparatus for producing composite products in which elongated members are oriented substantially parallel to the longitudinal direction of the composite products.
It is also an object of this invention to provide a continuous method and apparatus for manufacturing a composite product containing elongated members in which the members have an average vertical angle of not more than about 2.degree..